Procedural limitless terrain Guru

I have been using a multitude of different terrain assets to create my terrains and even though I have used many of the assets I am still having trouble making my terrains work for me. I am looking for a procedural limitless terrain that I can explore and at the same time place objects e.g. buildings or have animals spawn. What I require: I need someone with the knowledge on how to do this to help me create the achieved terrain with the littlest effort possible and also share your knowledge with me so in the future if I need to do this again I wont have issues. Please see my examples of the terrains I have created. Only people whom have worked in Unity and C need apply. If you're selected for this project, I do require your consent to add your name and if you've a website also please provide as your name will be added to my credits of my main project.